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Thu, 13 Mar 2025 00:01:42 -0700 (PDT) From: Akihiko Odaki Date: Thu, 13 Mar 2025 16:01:06 +0900 Subject: [PATCH net-next v10 03/10] tun: Allow steering eBPF program to fall back Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250313-rss-v10-3-3185d73a9af0@daynix.com> References: <20250313-rss-v10-0-3185d73a9af0@daynix.com> In-Reply-To: <20250313-rss-v10-0-3185d73a9af0@daynix.com> To: Jonathan Corbet , Willem de Bruijn , Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Michael S. Tsirkin" , Xuan Zhuo , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kselftest@vger.kernel.org, Yuri Benditovich , Andrew Melnychenko , Stephen Hemminger , gur.stavi@huawei.com, Lei Yang , Simon Horman , Akihiko Odaki X-Mailer: b4 0.15-dev-edae6 This clarifies a steering eBPF program takes precedence over the other steering algorithms. Signed-off-by: Akihiko Odaki --- Documentation/networking/tuntap.rst | 7 +++++++ drivers/net/tun.c | 28 +++++++++++++++++----------- include/uapi/linux/if_tun.h | 9 +++++++++ 3 files changed, 33 insertions(+), 11 deletions(-) diff --git a/Documentation/networking/tuntap.rst b/Documentation/networking= /tuntap.rst index 4d7087f727be..86b4ae8caa8a 100644 --- a/Documentation/networking/tuntap.rst +++ b/Documentation/networking/tuntap.rst @@ -206,6 +206,13 @@ enable is true we enable it, otherwise we disable it:: return ioctl(fd, TUNSETQUEUE, (void *)&ifr); } =20 +3.4 Reference +------------- + +``linux/if_tun.h`` defines the interface described below: + +.. kernel-doc:: include/uapi/linux/if_tun.h + Universal TUN/TAP device driver Frequently Asked Question =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D =20 diff --git a/drivers/net/tun.c b/drivers/net/tun.c index d8f4d3e996a7..9133ab9ed3f5 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -476,21 +476,29 @@ static u16 tun_automq_select_queue(struct tun_struct = *tun, struct sk_buff *skb) return txq; } =20 -static u16 tun_ebpf_select_queue(struct tun_struct *tun, struct sk_buff *s= kb) +static bool tun_ebpf_select_queue(struct tun_struct *tun, struct sk_buff *= skb, + u16 *ret) { struct tun_prog *prog; u32 numqueues; - u16 ret =3D 0; + u32 prog_ret; + + prog =3D rcu_dereference(tun->steering_prog); + if (!prog) + return false; =20 numqueues =3D READ_ONCE(tun->numqueues); - if (!numqueues) - return 0; + if (!numqueues) { + *ret =3D 0; + return true; + } =20 - prog =3D rcu_dereference(tun->steering_prog); - if (prog) - ret =3D bpf_prog_run_clear_cb(prog->prog, skb); + prog_ret =3D bpf_prog_run_clear_cb(prog->prog, skb); + if (prog_ret =3D=3D TUN_STEERINGEBPF_FALLBACK) + return false; =20 - return ret % numqueues; + *ret =3D (u16)prog_ret % numqueues; + return true; } =20 static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb, @@ -500,9 +508,7 @@ static u16 tun_select_queue(struct net_device *dev, str= uct sk_buff *skb, u16 ret; =20 rcu_read_lock(); - if (rcu_dereference(tun->steering_prog)) - ret =3D tun_ebpf_select_queue(tun, skb); - else + if (!tun_ebpf_select_queue(tun, skb, &ret)) ret =3D tun_automq_select_queue(tun, skb); rcu_read_unlock(); =20 diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h index 287cdc81c939..980de74724fc 100644 --- a/include/uapi/linux/if_tun.h +++ b/include/uapi/linux/if_tun.h @@ -115,4 +115,13 @@ struct tun_filter { __u8 addr[][ETH_ALEN]; }; =20 +/** + * define TUN_STEERINGEBPF_FALLBACK - A steering eBPF return value to fall= back + * + * A steering eBPF program may return this value to fall back to the steer= ing + * algorithm that should have been used if the program was not set. This a= llows + * selectively overriding the steering decision. + */ +#define TUN_STEERINGEBPF_FALLBACK -1 + #endif /* _UAPI__IF_TUN_H */ --=20 2.48.1